Solenoid devices or solenoids are linear actuator devices having a host of useful applications. For example, solenoids typically serve as a reliable type of on/off switch for precise operational control of various devices, e.g., electrical motors, valves, assembly robots, etc. Solenoids are ordinarily configured as electromechanical devices, although hydraulic and pneumatic variants exist that provide similar utility using different motive forces. A typical solenoid of the electromagnetic variety includes one or more coils of conductive wire surrounding a moveable piston portion or plunger, all of which is positioned within a solid ferromagnetic core. That is, a single-coil solenoid can be used in conjunction with a return spring, while a dual-coil solenoid can include each of a pull-in coil and a hold-in coil, with each coil dedicated to the specified function.
As with an electric motor, the passage of an electrical current though the solenoid coil induces a magnetic field around the coil. Selective application of the magnetic field thus moves the plunger in a particular and controllable manner, either by pushing or pulling the coil in a desired direction. That is, the induced magnetic field either attracts or repels the plunger, which is ordinarily constructed of iron or steel to facilitate this response. When the electrical current supplied to the solenoid is terminated, the induced magnetic field likewise terminates, thus allowing a return spring to move the plunger back to its original or de-energized position.
While the operational diagnosis of a solenoid can be provided using various means, such as by detecting the rate of a rise and fall in a measured solenoid current to determine if the solenoid is presently operating within specification, conventional methods can require the commitment of substantial computational resources, and/or the use of complex waveform or pattern recognition techniques. Additionally, such methods can be relatively expensive to implement due to the need for analog circuitry dedicated to the detection of electrical current transitions. Moreover, a determination of whether or not a particular solenoid is presently performing to specification does not provide a prognostic or predictive capability, and therefore can be less than optimal when used to predict remaining life of a solenoid. Such predictive value can be particularly useful when used in certain applications, such as but not limited to the monitoring of a solenoid used for controlling a vehicular starter motor.